Electroplating



Patented Aug. 28, 1945 I ELECTROPLAT ING Richard 0. Hull, Lakewood,Ohio, assignor to E. I.

du Pont de Nemours -& Company, Del., a corporation of Delaware NoDrawing.

12 Claims.

This invention relates to the electrodeposition of cadmium and is moreparticularly directed to processes and'compositions adapted to produce Icadmium deposits which are bright but subject to pitting, a small amountof a sulfonated vegetable oil being used as an anti-pit agent.

Wilmington, I

Application December 11, 1940, Serial 100,369,533

The development of the cadmium plating art has led in recent years tothe production of .brighter and brighter deposits and as a result theproblem of pitting has become important. Cadmium deposits produced bymost prior art practices have a matte surface orat the most are onlymoderately bright. With such deposits pitting is hardly noticeableunless it is unusually severe and it is rarely considered objectionable.With the bright, mirror-like cadmium deposits which the art is now ableto make even a small amount of pitting produces major blemishes. nbright deposits pitting is a major imperfection.

Pitting is apparently caused by any of anumber of things some of whichare known and some of which are not. One of the principal causes ofpitting is the presence of traces of thallium terious eifects whichresult from using it in addition agent concentrations. When used withaddition agents which lead to mirror-like deposits, a sulfonated.vegetable oil acts synergetically to produce brilliant deposits over awide current density range and the deposits are not water-repel- Y lentand they are free from pitting.

Any sulfonated vegetable oil may be used as an anti-pit agent and forexamples reference may be had to the Westbrook Patent 1,826,159. Saltssuch as monopole soap or a cadmium salt may be used as suggested in theWestbrook patent or the sulfonated oils may be added in solvents or,

in another suitable manner as suggested in the Westbrook patent.

'cording to the present invention are obtained which find their way intothe bath with the" cadmium. Pitting also seems to be a property ofcertain plating baths, some one or more of the bath constituentsprobably being to blame.

Now I have found that pitting may be decreased in cyanide-cadmiumplating baths by the inclusion of not substantially more than about 0.5gram per liter of a sulfonated vegetable oil' as an anti-pit agent. Itis more specifically preferred to use sulfonated castor oil.-

Westbrook in Patent 1,826,159 shows the use of sulfonated vegetable oilsas addition agents for cadmium plating. These sulfonated oilsaccordingto the practices of Westbrook are used in amounts equivalent to fromabout 5 to 15 grams per liter and deposits of good character areobtained as explained in the patient. Unfortunately, sulfonatedvegetableoils liave certain deleterious effects when used-in such amounts withother brightening agents which are capable .of producing trulymirror-like deposits. When Turkon Oil is present in addition agentamounts the cadmium plating bath has a limited bright current densityrange, the deposits produced are likely to be streaked, and thecadmiumsurface is water repellent. This last leads to particularly greatdiificulty if the deposits produced are to be bright-dipped or it theyare to receive a further electrodeposit.

When. not substantially more than about 0.5 gram per liter of asulfonated vegetable oil is used it serves as. an anti-pit without thedelewhen a sulfonated castor oil is used as an antipit agent and it isstill more specifically preferable to use the commercial grade ofsulfonated castor oil, Turkon Oil, mentioned in the Westbrook patent.

A cyanide-cadmium plating composition adapted to produce deposits whichare bright but subject to pitting is improved according to the presentinvention by the inclusion as an anti-pit agent of a sulfonated oil inan amount equiva-- lent to not substantially more than about 0.5 gramper liter. More specifically it is desirable to use from about 0.01 toabout 0.5 gram per liter and it is still more specifically preferred touse from about 0.05 to about 0.3 gram per liter ofa sulfonated vegetableoil. When not substantially more than 0.5 gram per liter of a sulfonatedvegetable oil is used as indicated the agent serves efiectively as ananti-pit but does not impart the deleterious effects'which result fromthe use of the material as an addition agent. It is further to be notedthat when a sulfonated vegetable oil is used at a concentration suitablefor an anti-pit according to the'present invention there upon thebrightness of is no substantial efiect The anti-pit agents of thisinvention may advantageously be used to prevent pitting in anycyanide-cadmium plating system, but the best results are obtained whenthe agents areused in conjunction with an addition agent which promotesthe formation of. brilliant, mirror like deposits. While any additionagent may be used, particularly good results have been obtained usingisoamketaldoresins as set out in Henricks 2,085,750

and as further described in Henricks 2,085,747,

Henricks 2,085,748, Henricks 2,085,749, Hull I 2,085,754, Hull.2,090,049, and 'LutZ 2,097,630.

While any isoamketaldoresin may be used, it is By far the best resultsac-- preferred to use amketaldoresins, while still more specifically itis preferred to use amaldacets. It is still more specifically preferredto use the antipit agents of this invention with cyalda'cets asspecifically set out in Henricks 2,085,747.

Metal brighteners as shown in the Westbrook Patent 1,681,500 such asiron, cobalt, and nickel may be used in baths of the present invention.

It is preferred to use cobalt and this or the other of the metals may beused as shown in the abovementioned patents to Westbrook, Henricks,Hull,

or Lutz.

The anti-pit agents of this invention are used in cyanide-cadmiumplating baths and any bath may be employed. Illustrative ofcyanide-cadmium plating baths are those shown in the Westbrook,.I-Ienricks, Hull and Lutz patents above mentioned.

The anti-pit agents of this inventiorrmay most advantageously beincluded in compositions com- EXAMPLE A cyanide-cadmium platingbath wasmade-up with the following: a

Grams per liter Sodium cyanide (NaCN) 130 The addition agent employed isthe concentrated agent of Example I of Henricks 2,085,747

the agent being used in very much the same fashion as in Example III ofthe patent. Using the above-described bath brilliant mirror-likedeposits were obtained in a barrel plating installation and the workproduced was-free from visually discernible pits. g

A similar bath was made up using additionally grams per liter of cobaltsulfate (COSOr'IHaO) and excellent result were btam a sun Platinginstallation.

While I \have described certain illustrative products in the foregoing,it will be understood that one skilled in the art may readily employ asulfonated vegetable oil as an anti-pit agent in cyanide-cadmium platingbaths in a variety ,of ways without departing from the spirit of thisinvention.

I claim:

1. In a process for the electrodeposition of cadmium from an aqueouscyanide-cadr'iium bath, the step comprising 'eflecting deposltim in thepr a e of anisoamketaldoresin and t substantially more than about 0.5gram per liter of a sulionated vegetable oil.

2. In a process for the electrodeposition oi cadmium froman aqueouscyanide-cadmium bath, the step comprising reflecting deposition in thepresence of an amaldacet and not substantially more than about 0.5 gramper liter of a sulfonated vegetable oil.

3. In a process for the electrodeposition of cadmium from an aqueouscyanide-cadmium bath, the step comprising eflecting deposition in thepresence of a cyaldacet, a compound of co- 1 halt, and not substantiallymore than about 0.5 gram per liter of a sulfonated vegetable oil.

4. In a process for the electrodeposition of "cadmium from an aqueouscyanide-cadmium the presence of an amaldacet and not substanbath adaptedto produce deposits which are bright but subject to pitting, the stepcomprising eflecting deposition in the presence of an anti-pit agentcomprising not substantially more than about 0.5 gram perv liter ofsulfonated castor oil.

5 In a process for the electrodeposition of cadmium from an aqueouscyanide-cadmium bath, the step comprising efiecting cleposition'intially more than about 0.5 gram per liter of sulfonated castor oil.

6. In a process for the electrodeposition of cadmium from an aqueouscyanide-cadmium bath, the step comprising eflecting deposition in thepresence of a oyaldacet and about 0.1 to 0.5 gram per liter ofsulionated castor oil.

'7. In a process for the electrodeposition of cadmium from an aqueouscyanideecadmium bath, the step comprising effecting deposition in I thepresence of a compound of a metal selected Cadmium oxide (CdO) 43'Sodium sulfate (Nazsol) Addition agent 3 2 Turkont oil 0.2

from the group consistingof cobalt, nickel, and copper and about 0.1 to0.5 gram per liter of sulfonated castor oil.

8. In a process for the electrodeposition of cadmium from an aqueouscyanide-cadmium bath, the step comprising effecting deposition in thepresence of a cyaldacet, a cobalt compound, and about 0.5 to 0.3 gramper liter of sulfonated castor oil.

9. A composition of matter adapted to improve the character of depositobtainable from cyanide cadmium plating baths comprising about two partsby weight of a cyaldacet and about 0.01 to 0.5 part by weight of asulfonated castor oil.

10.. A composition of matter adapted to lm-'- prove the character ofdeposit obtainablefrom cyanide-cadmium plating baths comprising abouttwo parts by weight of a cyaldacet and about 0.05 to 0.3 part byweightof a sulfonated castor 11. A composition of matter adapted to improvethe character of deposit obtainable from cyanide-cadmium plating bathscomprising about two parts by weight oi an amaldacet and about 0.01 to0.5 part by weight of a sultonat'ed vezetable .011.

12. A composition ofmatter adapted to improve the character of depositobtainable from' cyanide-cadmium plating baths. comprising about a twoparts by weight of a cyaldacet and 0.2-

par castor oil.

by weight of sulfonated RICHARD OJHULL.

